In a conventional case that inventory of articles, e.g., clothes, is carried out in a shop, a handy type RFID tag reader/writer may be used to collectively read out data of RFID tags which are respectively attached to clothes packed in a box or on a shelf.
In such a case, it is an ideal that data of all of the RFID tags attached to clothes can be read out from the outside of the box or shelf. However, it may be difficult in practice due to overlap of antennas of a plurality of RFID tags or an antenna of RFID tag touching a metal. It may also adversely affect the reading accuracy of the RFID tag reader/writer.
According to the above-described circumstances, there is a desire that an antenna of the RFID tag reader/writer is inserted into the box in which clothes are packed and data of RFID tags attached to clothes are collectively read out by the inserted antenna as much as possible. To achieve the above desire, it is required to minimize the antenna of the RFID tag reader/writer and to control the radiation direction of the antenna.
However, the RFID reader/writer generally uses a patch antenna which radiates radio wave in a single direction. Therefore, data of RFID tags only located at a side in a radio wave radiation direction of such a patch antenna can be read out even if the antenna is inserted into the packed cloths in the box.